verb

• (ambitransitive) To make a brief, basic drawing.
  "I usually sketch with a pen rather than a pencil."
• (transitive) To describe briefly and with very few details.
  "He sketched the accident, sticking to the facts as they had happened."

noun

• (informal) An amusing person.
• (slang, Ireland) A lookout; vigilant watch for something.
  "to keep sketch"
• (UK) A humorous newspaper article summarizing political events, making heavy use of metaphor, paraphrase and caricature.
  "A very capable journalist, he wrote the Parliamentary sketch for the Pall Mall and the Westminster Gazette for several years."
• (category theory) A formal specification of a mathematical structure or a data type described in terms of a graph and diagrams (and cones (and cocones)) on it. It can be implemented by means of “models”, which are functors which are graph homomorphisms from the formal specification to categories such that the diagrams become commutative, the cones become limiting (i.e., products), the cocones become colimiting (i.e., sums).

adj

• (informal) Sketchy, shady, questionable.
  "You call at 9 am on a Saturday, lucky I'm even awake. [...] Then expect me to pick you up at a gas station near a loony bin, that's sketch. I don't even want to ask what you're doing."